[Translated article] Risk of a Second Skin Cancer in a Cohort of Patients With Nonmelanoma Skin Cancer – Basal Cell Carcinoma or Squamous Cell Carcinoma – Treated With Mohs Micrographic Surgery: A National Prospective Cohort Study

Riesgo de aparición de segundas neoplasias cutáneas en una cohorte de pacientes diagnosticados de carcinoma queratinocítico (carcinoma basocelular y carcinoma epidermoide) tratados con cirugía de Mohs. Estudio de cohortes prospectivo nacional


Patients with nonmelanoma skin cancer (NMSC)—ie, basal cell carcinoma (BCC) or squamous cell carcinoma (SCC)—have an increased risk of developing a second skin cancer. The aim of this study was to describe the frequency, incidence per 1000 person-years, and predictors of a second skin cancer in a cohort of patients with NMSC treated with Mohs micrographic surgery (MMS).

Material and methods

Prospective study of a national cohort of patients with NMSC who underwent MMS at 22 Spanish hospitals between July 2013 and February 2020; case data were recorded in the REGESMOHS registry. The study variables included demographic characteristics, frequency and incidence per 1000 person-years of second skin cancers diagnosed during the study period, and risk factors identified using mixed-effects logistic regression.


We analyzed data for 4768 patients who underwent MMS; 4397 (92%) had BCC and 371 (8%) had SCC. Mean follow-up was 2.4 years. Overall, 1201 patients (25%) developed a second skin cancer during follow-up; 1013 of the tumors were BCCs (21%), 154 were SCCs (3%), and 20 were melanomas (0.4%). The incidence was 107 per 1000 person-years (95% CI, 101–113) for any cancer, 90 per 1000 person-years (95% CI, 85–96) for BCC, 14 (95% CI, 12–16) per 1000 person-years for SCC, and 2 (95% CI, 1–3) per 1000 person-years for melanoma. More men than women developed a subsequent skin cancer (738 [61%] vs 463 [39%]). The main risk factors were a history of multiple tumors before diagnosis (relative risk [RR], 4.6; 95% CI, 2.9–7.1), immunosuppression (RR, 2.1; 95% CI, 1.4–3.1), and male sex (RR, 1.6; 95% CI, 1.4–1.9).


Patients have an increased risk of developing a second tumor after MMS treatment of NMSC. Risk factors are a history of multiple tumors at diagnosis, immunosuppression, and male sex.

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